From 7b4cc5d8411bd4e9d61d8714f53859740cf830c2 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Mon, 8 Jul 2013 16:01:12 -0700 Subject: ipc: move locking out of ipcctl_pre_down_nolock This function currently acquires both the rw_mutex and the rcu lock on successful lookups, leaving the callers to explicitly unlock them, creating another two level locking situation. Make the callers (including those that still use ipcctl_pre_down()) explicitly lock and unlock the rwsem and rcu lock. Signed-off-by: Davidlohr Bueso Cc: Andi Kleen Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/sem.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) (limited to 'ipc/sem.c') diff --git a/ipc/sem.c b/ipc/sem.c index 92ec6c69bab5..b4b892b5c5f8 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1289,39 +1289,44 @@ static int semctl_down(struct ipc_namespace *ns, int semid, return -EFAULT; } + down_write(&sem_ids(ns).rw_mutex); + rcu_read_lock(); + ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd, &semid64.sem_perm, 0); - if (IS_ERR(ipcp)) - return PTR_ERR(ipcp); + if (IS_ERR(ipcp)) { + err = PTR_ERR(ipcp); + /* the ipc lock is not held upon failure */ + goto out_unlock1; + } sma = container_of(ipcp, struct sem_array, sem_perm); err = security_sem_semctl(sma, cmd); - if (err) { - rcu_read_unlock(); - goto out_up; - } + if (err) + goto out_unlock1; - switch(cmd){ + switch (cmd) { case IPC_RMID: sem_lock(sma, NULL, -1); + /* freeary unlocks the ipc object and rcu */ freeary(ns, ipcp); goto out_up; case IPC_SET: sem_lock(sma, NULL, -1); err = ipc_update_perm(&semid64.sem_perm, ipcp); if (err) - goto out_unlock; + goto out_unlock0; sma->sem_ctime = get_seconds(); break; default: - rcu_read_unlock(); err = -EINVAL; - goto out_up; + goto out_unlock1; } -out_unlock: +out_unlock0: sem_unlock(sma, -1); +out_unlock1: rcu_read_unlock(); out_up: up_write(&sem_ids(ns).rw_mutex); -- cgit v1.2.3-70-g09d2